Method of producing a packaging container comprising a container body of thermoplastic material

ABSTRACT

A thermoplastic container is provided with a lining of metal foil coated with thermoplastic material which is folded or pleated to fit the container snugly and is heat sealed thereto. Suitable covers or lids are provided so that the final container is most suitable as to cost, weight, impermeability and finally as to customer appeal.

United States Patent Inventor Anders Ruben Rausing Blentarp, Sweden Appl. No. 758,433 Filed Sept. 9, 1968 Patented Oct. 26, 1971 Assignee Sobrefina SA Fribourg, Switzerland Priority Sept. 25, 1967 Sweden 13129/67 METHOD OF PRODUCING A PACKAGING CONTAINER COMPRISING A CONTAINER BODY OF THERMOPLASTIC MATERIAL 1 Claim, 5 Drawing Figs.

US. Cl 156/287,

156/286,156/293 Int. Cl B29c 17/06 Field of Search 229/93;

References Cited Primary Examiner Benjamin R. Padgett Assistant Examiner--Gary G. Solyst A!t0rneyPierce, Scheffler & Parker ABSTRACT: A thermoplastic container is provided with a lining of metal foil coated with thermoplastic material which is folded or pleated to fit the container snugly and is heat sealed thereto. Suitable covers or lids are provided so that the final container is most suitable as to cost, weight, impermeability and finally as to customer appeal.

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PATENTEDUET 26 men SHEET 2 BF 2 5 v g .1 a Q METHOD OF PRODUCING A PACKAGING CONTAINER COMPRISING A CONTAINER BODY OF THERMOPLASTIC MATERIAL This invention is concerned with a method of producing a packaging container comprising a container body of thermoplastic material and a metal foil lining inserted into the container body. The invention is further concerned with a device for carrying out the operation in accordance with the above and also with a packaging container produced in accordance with this method.

It has for a long time been the objective within the packaging industry to develop types of package that solve in the best way the specific problems which arise within packaging technology. A throwaway package shall e.g., be inexpensive but it shall also be well suited to its contents, so that it protects the contents in the best way both mechanically and otherwise. The package shall further appeal to the customer, i.e., the contents shall be easily accessible when the customer wants to make use of them. It shall further have a low weight and be well suited to storage in available spaces. These requirements that modern packages have to meet have resulted in the development of a great number of different types of package, each of which has been suited to one special type of contents.

Within the canning industry, packaging materials other that sheet metal have not been used very much up till now, which material exhibits many properties suited to canning. Sheet metal is e.g., very impermeable and has very satisfactory mechanical strength. The drawbacks of sheet metal packaging are that it is comparatively expensive and besides so strong mechanically that sheet metal packaging containers cannot be opened without the use of special aids in the shape of tin openers or keys. Glass packages in the shape ofjars or bottles have so far been the predominant method of packaging for aerated liquids, e.g., aerated drinks, beer, etc. The impermeability of glass is certainly remarkable, but glass packaging is heavy, expensive and comparatively easy to damage, and attempts have therefore been made to find a method of packaging which will replace sheet metal and glass for the above groups of products. The solutions which have so far been put forward in this connection entail a transition to sheet metal or glass packages which have a lesser thickness. Attempts have also been made in many places to use plastic packages as an alternative to sheet metal or glass packages, but these attempts have come to nothing as a result of the fact that known plastic materials that can be used economically have an impermeability that is too unsatisfactory for use for either canned goods or aerated drinks. In the case of canned goods, oxygen difiuses into the package, as a result of which the contents are oxydized and in the case of aerated drinks, carbon dioxide diffuses out of the package.

It can be stated that there exists a need for a cheaper, lighter and easier-to-open packaging container that has sufficient impenneability, and this invention gives directions concerning such a packaging container as well as the method of its production.

The invention is thus concerned with a method of producing a packaging container which comprises a container body of thermoplastic material and a metal foil lining inserted into the container body. The invention is characterized by a blank, conveniently of round shape, of a metal foil coated with thermoplastic material being, by means of a tool, pressed into the said container body and by the plastic coating of the metal foil, at least along a continuous joint, being heat sealed to the container body around its opening. The invention is further characterized by the blank, or roundel, being made to assume, through being folded, the shape of the container body, and by the said folding and shaping being brought about by the blank, through the application of vacuum, being sucked against the tool which has longitudinal grooves that facilitate the forma- Lion of the folds, the grooves being capable of connection to a source of vacuum.

Packaging containers which have been produced in accordance with the invention have the advantages of the con-- ventional cans, i.e., they have very satisfactory impermeability as a result of the incorporation of a metal foil layer in the wall of the container. They can also be made sufficiently stiff mechanically by surrounding the packaging container by e.g., a sleeve of cardboard or plastic. The package will be lighter than earlier conventional preserve packages, and also considerably easier to open, since it is possible to break through the walls of the package with a much simpler tool, or the package may quite simply be fitter with an opening device that makes a special opening tool unnecessary.

One constructional form will be described in the following by reference to the attached diagrammatic drawings, of which: FIG. I shows two views of a vacuum tool in partial section,

FIG. 2 shows the thermoplastic container body which has been placed in a; holder and is ready to receive the metal lina FIG. 3 shows how the metal lining is inserted into the container body,

FIG. 4 shows a cross section of the completed packaging container and finally FIG. 5 shows a flat blank which is to be inserted into the conical top portion of the container.

For the sake of clarity, we will first of all define the terminology used as regards the packaging container itself. The term container body thus refers in this case to a preproduced hollow body of thermoplastic material. The layer of metal foil inserted into the container body is termed lining", the container body and the lining together forming a packaging container that may in a suitable manner be provided with some kind of closure covering the opening of the container.

FIG. I shows a partial section of a folding tool 3 which consists of a cylindrical portion and a curved bottom portion. The tool has a number of pleating grooves 5 which extend parallel along the cylindrical portion and towards the center part of the bottom portion, which grooves through ducts 9 are connected to the inside of the tool, which in turn is connected to a source of vacuum or ofgas under pressure by means of tube 7. The upper portion of the tool shown is covered by a sheet 6 around the outside edge of which there is fitted a ring-shaped welding unit 8. There is on the curved bottom portion of the tool a central suction hole 10 by means of which the tool is capable of attaching to itself flat blanks. 86 104 insertion of the lining into the container body is effected in the following way: the preproduced container body 11 shown in FIG. 2 is inserted into an outer holder 13 which supports the sides of container body 11, the outward-folded flange I2 of container body 11 being preferably made to rest on the top of holder 13. The material from which the lining is to be made consists of preproduced roundels l of metal foil, preferably aluminum foil, coated with thermoplastic, the coating consisting of a layer 2 of polyethylene or polypropylene, or some varnish that is suitable for lamination.

The lining operation is begun by the inside of tool 3 through tube 7 being connected to a source of vacuum and by the tool being thereafter brought in contact with a preproduced lining blank. This preferably done by the tool being lowered towards a pile of plastic-coated roundels of aluminum foil. When the center portion of the tool has come into surface contact with the uppermost roundel in the pile, this is attached by suction to the tool by means of suction hole I0. Tool 3 can now be lifted up and will then take with it the uppermost roundel in the pile. While the inside of the tool 3 is still connected to a source of vacuum, the tool is positioned above the container body 11 inserted into holder 13 and is lowered into this. When tool 3 is lowered down into container body 11, the roundel of metal foil is folded up against the outside of the tool and is sucked into the grooves 5 in the tool. This suction of the roundel 1 of metal foil into grooves 5 is accompanied by the formation of folds in the roundel of metal foil, the design of grooves 5 being such that the folds formed are even.

When the roundel l of metal foil has been sucked against tool 3 as shown in FIG. 3a and has been sucked into grooves 5 in tool 3, as shown in FIG. 3b, and when tool 3 has been brought to the final position shown in FIG. 30, the inside of tool 3 is connected to a source of gas under pressure through the tube 7. Instead of being sucked into grooves 5, the lining l is now forced out of the grooves into a position shown in FIG. 3d, i.e., the lining forms a largely even inside coating in container body 1 1. in order that the contact between lining l and the inside of container body 1 1 may be further improved, it is an advantage if, in conjunction with lining 1 being pressed out of grooves 5 through the action of gas under pressure, tool 3 is rotated by means of shaft 14. This rotation of the tool also results in the extraction of the tool out of the container body being easier to achieve without the lining being withdrawn as well.

While the tool 3 is still inside container body 11, the plastic layer 2 of lining l is welded to container body 1 1 along a continuous sealing zone 17 in the vicinity of the opening of container body 11. This welding or sealing of the plastic layer 2 of lining 1 to container body 11 is carried out with the aid of the ring-shaped sealing unit 8 fitted around the upper part of tool 3. The welding operation may be effected by heat being produced in the sealing unit, and by this heat being then conducted by way of the metal foil layer to the plastic layer and to the wall of container body 11, and by so much heat being supplied that the plastic layer 2 of the lining is fused with the inner surface of the container body 11. The heat required for this fusion may also be produced by means of ultrasonic waves or by high-freqency methods. The choice of the welding method used depends on the properties of the material. Thus, it may sometimes be difficult to conduct a sufficiently large quantity of heat through a metal foil layer, since the cooling area of the metal foil is large. High-frequency welding would also seem not to be directly applicable to the sealing of a laminate comprising a layer of metal foil, since the heat quantity produced tends to be concentrated to the layer of metal foil. The most suitable welding method in the present case is probably ultrasonic welding, i.e., mechanical oscillations of ultrasonic frequency are generated in sealing unit 8 which is then brought into contact with the laid-up material layers which are to be welded together; or also impulse sealing, i.e., sealing with the aid of a unit that by means of impulses of current is heated to scaling temperature. The heat generated in the plastic material shall be sufficient for the materials to be welded together into an impermeable and homogeneous joint.

The packaging container, ie, the container body 11 provided with the lining, that has been formed can be closed by a thin sheet of material being placed over the opening of the container and welded to the flange 12 of the container body. In order that this cover shall have the same impermeability as the rest of the packaging container, it should also contain a layer of metal foil. In order to enable the cover material to be heat sealed to the packaging container along the flange 12, the cover material is provided with a coating of plastic which can be welded against the upper side of flange 12. In order that such welding of the cover material should be possible, it is naturally necessary that the metal foil lining l in the packaging container should not extend above the plane of the opening of the container, since any metal foil that may have been folded out over flange 12 would make it impossible to effect a seal between the cover material and the said flange.

The closure of the packaging container may also be effected by the opening of the container body 11 being covered, by means of a conical or hemispherical part that has a flange corresponding to flange 12 of the container body, being placed over the opening of the container body in such a way that the flanges coincide. The two flanges can now be welded together. a bottle-shaped container being obtained.

In order that the impermeability characteristics of the packaging container should not be made worse, the packaging container with the conical upper part 16, shown in FIG. 4, should be provided with a lining is of metal foil, which is sealed to the conical part 16 along continuous weld joints 17, the conical part being preferably of the same material as the container body 1 1. The metal foil linin 15 can in the case of the packaging container shown in FIG. be made as a flat or:-

cular sector consisting of a metal foil coated with plastic. By means of the edges of the sector shown in FIG. 5 being brought together, a conical shape is formed that can be inserted into the conical upper part 16. It is also of importance here that the metal foil lining should not be allowed to project beyond the flange 18.

The constructional example of the invention shown here is only intended as an illustration of the idea behind the invention, and it is thus possible, within the framework of the invention, to modify both the shape of the container body and the shape of the part 16 covering the opening of the container body. The invention has proved to be very valuable and is the first solution that we know of, of the problem of obtaining the same impermeability characteristics in a packaging container of plastic as in packaging container of sheet metal or glass known earlier.

I claim:

1. A method for producing containers comprising pressing a blank of metal foil into a thermoplastic container body having a cylindrical body portion, a spherical bottom portion and top circular opening, said pressing being carried out by means of a mandrellike tool having a plurality of grooves extending axially along the cylindrical outer surface thereof and towards the center at a bottom spherical portion thereof, said metal foil being coated with a thermoplastic material on the outer side thereof facing the thermoplastic container body, applying a vacuum to the inner side of the blank of metal foil through openings in the grooves in the walls of the tool to shape the blank of metal foil to the tool and to shape the blank to the container body by creating axial folds in the foil in the grooves of the tool, subsequently applying pressure to the inner side of the blank of metal foil through openings in the grooves in the walls of the tool while rotating the tool about is axis so as to release the blank from the tool while overlapping at least a portion of each of the axial folds and while positioning the blank within the container body, and heat-sealing the thermoplastic coating on the foil to the thermoplastic container body at least continuously about the circular opening of the container body. 

